The objective of the proposed research is to use the mouse as an animal-model to investigate inherited human disorders that affect growth. The research will concentrate on three disorders: (1 and 2) the ateliotic dwarfisms, familial-panhypopituitarism and isolated- growth-hormone-deficiency type I; and (3) familial-vitamin D-resistant- rickets. Mouse models for ateliotic dwarfisms will be investigated by approaches in vivo and in vitro to determine whether the site of mutated gene action resides in the pituitary or hypothalamus. Methods include a developmental study of pituitary glands by specific antibody localization of hormone-producing cell types and hormone assays, reciprocal transplantation of pituitaries, histological examination of peripheral endocrine glands, live-animal measures, and experiments on hormone production and release in culture. Hormone levels in plasma, pituitaries, and incubation media will be determined by bioassays and radioimmunoassays. The mouse model for familial vitamin D-resistant rickets will be investigated by approaches in vivo and in vitro to determine whether the inborn-error-of-metabolism involves vitamin D metabolism. Methods include a developmental study of the disorder,reciprocal transplantation of levels of phosphate, calcium, and alkaline phosphatase will be measured; transport of calcium and phosphate systems will be studied; and the ability to produce various vitamin D metabolites will be determined by studies in vivo and in vitro.